1. Field of the Invention
The present invention relates to a novel phosphor of green luminescence and more particularly, to the phosphor of green luminescence containing Tb(terbium) as an activator and a perovskite-structure(CaSnO.sub.3) as a host compound, which may emit a luminescent spectrum in the visible range, when excited by electron beam. The phosphor of green luminescence of this invention with better luminescence than the conventional phosphors has been widely applicable to the display industry including an electronic display such as cathode-ray tube(CRT) and field emission display(FED) etc., in spite of the fact the use of Tb, a high-priced rare earth element, is minimized without any sulfur(S) in its chemical composition.
2. Description of the Related Art
Hitherto, many researches have focused on RGB phosphors for an electronic display to emit the colors, which are core materials in the display industry. To this end, the phosphors of various host compounds have been intensively studied in phosphors using Tb(terbium), a rare earth element as an activator.
In general, the phosphor induced by Tb activator emits both a blue luminescent spectrum mainly based on the transfer of .sup.5 D.sub.3 .fwdarw..sup.7 F.sub.j (j=1.about.6) and a green luminescent spectrum mainly based on the transfer of .sup.5 D.sub.4 .fwdarw..sup.7 F.sub.j (j=1.about.6) in the visible range. More specifically, it has been reported that a spectrum in the blue range at a low concentration of Tb is observed and as the concentration of Tb increases, only a spectrum of the green range is observed, while a spectrum in the blue range disappears[Chem. Phys. Lett., 113,387 (1985)].
Examples of the phosphors using Tb, which are still under review for commercial use, include Tb-activated yttrium silicate phosphor (Y.sub.2 SiO.sub.5 :Tb), Tb-activated YAG phosphor (Y.sub.3 Al.sub.5 O.sub.12 :Tb) and Tb-activated yttrium oxide phosphor (Y.sub.2 O.sub.3 :Tb).
The optimum concentrations of Tb used in the phosphors expressed by Y.sub.2 SiO.sub.5 :Tb, Y.sub.3 Al.sub.5 O.sub.12 :Tb, and Y.sub.2 O.sub.3 :Tb are about 2.5 mol %, 5 mol % and 7 mol %, respectively. These relatively large amounts reflect that since the solid solubility limit of these host compounds on Tb in the phosphors is high, each host compound has a larger capacity of incorporating the Tb activator.
However, the conventional Tb-activated phosphors are not sufficient in emission intensity in spite of its a higher content of Tb in its chemical composition. Thus, there is a need that the phosphor with better luminescence characteristics should be developed together with a technology to lessen the use of high-priced Tb in the economic aspect.
In addition, when phosphors are under consideration for use in an electronic display such as field emission display, the conventional phosphors of green luminescence containing some sulfur compounds expressed by ZnS:Cu,Al; (Zn,Cd)S:Cu and ZnS:Cu,Au,Al phosphors etc. are known to contaminate the emitter tips by the release of corrosive, sulfur-related gases(e.g., SO.sub.2, SO) under prolonged electron bombardment [J. Electrochem. Soc., 136(6), 1819 (1989)]. Thus, an alternative use of new oxide phosphor is required as a phosphor of green luminescence.